1. Field of the Invention
The present invention relates to a composition which is provided in the form of a W/O/W triple emulsion and to its applications in the cosmetic and dermatological fields, in particular for the controlled release of active agent, more particularly of water-sensitive and/or oxygen-sensitive active agent and of acidic active agents, in particular for the purpose of cleaning and/or treating and/or protecting the skin and/or mucous membranes and/or keratinous fibers.
2. Background of the Invention
It is known to introduce active agents into cosmetic and/or dermatological compositions for the purpose of contributing specific treatments to the skin, for example for combating drying, ageing or pigmentation of the skin, for treating acne or certain skin diseases (eczema, psoriasis), for combating excess weight, for promoting restructuring of the skin or its cell renewal, or for coloring the skin.
For example, ascorbic acid (or vitamin C) is known to stimulate the growth of the connective tissue and in particular that of collagen. It also makes it possible to strengthen the defenses of cutaneous tissue against external attacks, such as ultraviolet radiation or pollution. Ascorbic acid is also used for removing blotches and pigmentation of the skin and also for promoting healing of the skin.
In addition, it is known that the application of hydroxy acids to the skin makes it possible in particular to combat cutaneous ageing and certain disorders of the skin, such as acne.
Furthermore, triple emulsions are known to be potentially advantageous in the controlled release of active agents. In particular, they make it possible to protect sensitive active agents against external agents which are harmful to the stability of these active agents, such as water or oxygen. Water/oil/water (W/O/W) emulsions are particularly advantageous because the inner and outer aqueous phases are separated by an oily layer. An active agent encapsulated in the inner phase can thus be maintained outside the outer phase (see article by Dahmer Tagawa, 19th IFSCC Congress, Sydney, 1996). Thus, EP-A-779,071 discloses a W/O/W emulsion containing a water-sensitive active agent.
Unfortunately, certain active agents and in particular acidic active agents, because of their acidity, destabilize the triple emulsions containing them, in particular when the outer aqueous phase is gelled. This lack of stability is reflected by a phase separation and/or the production of a simple O/W emulsion instead of a triple emulsion.
Thus, the need remains for a stable W/O/W emulsion capable of containing acidic cosmetic and/or dermatological active agents.